True Ghost Achievement
Get 10 consecutive kills in one Quick Match without dying
Probably one of the hardest achievement to unlock on the multiplayer. At least for me took me forever. I personally did this using the Scout class on the Pipeline level during a Conflict match. I just took cover behind a wall on the second floor, wait to become invisible and press to aim behind cover and to bring up your scope and snipe the enemies as they try to capture the objective.
Basically choose a class your comfortable with and try to get a map you know your way around. Or if your lucky enough to find a match with some people that aren't very good at this game, focus on killing them, then capturing objectives. Good luck with this one!